This invention concerns a fuel tank and the general purpose engine equipped with the same.
Fuel tanks for automobile engines or the sort of general purpose engines used in farm equipment are produced by pressing an upper portion and a lower portion out of sheet metal and joining the two with a flange.
Fuel tanks for automobiles are generally installed under the floor panel in the rear part of the body. On the upper surface of the fuel tank are several grooves running from front to rear to accommodate the drive shafts and the live axle which transmits the steering force. Water tends to accumulate in these grooves, causing the tank to rust.
The fuel tank shown in FIGS. 5 and 6 is designed to prevent this problem from occurring. The design of this automobile fuel tank is disclosed in the publication (Kokai) of Japanese Utility Model 63-159324. FIG. 5 is a plan view and FIG. 6 is a cross section taken along line Cxe2x80x94C in FIG. 5.
In FIGS. 5 and 6, 1 is the fuel tank; 11 is the gearbox to operate the rear wheels which is installed behind fuel tank 1; 12 and 13 are the pinion shaft and the rack shaft; 14 is the universal joint; and 15 is the shaft to transmit the steering force.
On the upper surface of the fuel tank 1 there is a groove 5 which traverses the tank from front to rear. This groove 5 accommodates the shaft 15, universal joint 14 and pinion shaft 12. The upper surface 2 of the tank is divided in two by the groove 5. On the rear portion of this surface, on either side of groove 5, are expanded portions 3, which help provide the necessary volume by protruding above the rest of the tank. The surface of the fuel tank 1 is coated with a rust-proofing substance. In the drawing, 4 is the fuel inlet; 31 is the surface where the fuel pump is mounted; 32 is the surface where the gauge unit is mounted; and 41 is the vent pipe.
The bottom of the groove 5, as can be seen in the lateral view in FIG. 6, comprises a long inclined surface 6 which slants down toward the front of the tank and a short inclined surface 7 which slants down toward the rear of the tank. Together, the two inclined surfaces give the groove a convex bottom. A resin coating is applied to the surface of the groove. Its apex 8 is located between the two expanded portions 3 at the rear of the tank. If any water should get into the groove 5, it will discharge along forward-sloping surface 6 and rearward-sloping surface 7 until it is discharged onto the ground at the edges of the tank.
Leaving automobile fuel tanks for a moment, let us turn our attention to the fuel tanks used in small general purpose engines. In these engines, the fuel inlet is generally on the top of the tank. When this type of fuel tank is filled, some of the fuel is liable to overflow from the fuel inlet or drip from the filling nozzle and spread over the surface of the tank. If it touches the cylinder, which is extremely hot, it may start on fire; if it comes in contact with an electrical component, it may lead to malfunctioning.
To prevent such problems, a design for the fuel tank of a small general purpose engine has been proposed such that there is a groove near the fuel inlet to carry off any spilled fuel. The groove is slanted like that shown in FIGS. 5 and 6 so that it can discharge the fuel in a given direction onto the ground.
We shall discuss such a fuel tank belonging to the prior art with reference to FIGS. 7 and 8.
FIG. 7 is a front view of a general purpose engine with the fuel tank described above; FIG. 8 is a plan view of the same engine. In FIGS. 7 and 8, 50 is the engine; 51 is the engine body; 52 (see FIG. 8) is the output shaft; 53 is the muffler; 54 is the air cleaner; 55 is the carburetor; 56 and 57 are the throttle and choke levers; 58 is the recoil starter; and 59 is the grip of the recoil starter 58. 61 is the fuel tank; 60 is the fuel cock which is connected to the fuel tank 61; 62 is the gauge unit; 63 is the label; and 64 is the cap for the fuel inlet. The cylinder shaft (not pictured) of engine body 51 is canted from below muffler 53 toward output shaft 52.
Fuel tank 61 comprises two pan-shaped portions which are pressed from thin copper sheeting. These portions are seam-welded along flange 61a, which runs along the periphery of the tank. The upper surface of the tank is level in the center and inclines slightly toward the edges. The area around fuel inlet 61b (see FIG. 7) in the center of the tank forms a depression bounded by conical surface 61c. The bottom of the depression extends toward recoil starter 58 and is inclined downward by a suitable amount toward the outer edge of the tank. Its cross section is a trapezoid with downward-sloping sides, which we shall call depression 61d. The end of this depression opens onto recoil starter 58. Any fuel spilled at the fuel inlet is thus conducted toward recoil starter 58 and sluiced off the top of the tank.
In the device pictured in FIGS. 7 and 8, the hot cylinder and the electrical components are concentrated on the left side of fuel tank 61. It is crucial, then, to prevent any spilled fuel from entering this region.
A fuel tank 61 for a general purpose engine like that shown in FIGS. 7 and 8 has a depression 61d around the fuel inlet on the top of the tank, and the bottom of the depression is angled toward recoil starter 58. If fuel overflows during fueling or drips from the nozzle onto the tank, it will flow in a sideways direction, either to the left or right of the tank, and be discharged out of depression 61d. 
Similarly, with the fuel tank 1 for an automobile engine which is pictured in FIGS. 5 and 6, the spilled fuel which discharges into depression 5 goes down to the edge of the tank and is routed horizontally along the flange.
If this horizontally-discharging spilled fuel should come in contact with the hot cylinder, it may combust; if it should come in contact with electrical components, their function may be impaired or they may fail. And because both the tanks 61 and 1 consist of two halves made of thin copper sheeting, they tend to experience vibration and noise due to sympathetic vibration with the engine.
In view of the above-described problems inherent in the prior art, the first object in designing this invention is to improve the safety of the engine by preventing fuel which overflows the inlet or splashes onto the top of the tank during fueling from dripping down onto the hot cylinder or coming in contact with any electrical component.
The second object is to provide an engine whose fuel tank will not be subject to vibration or its resultant noise.
The invention which solves these problems is a fuel tank comprising an upper and lower half which are joined with a flange, with the fuel inlet on the top of the tank.
This fuel tank is distinguished by the fact that the upper portion of the tank has a depression on its upper surface which contains the fuel inlet and which angles downward toward one side of the tank. A gutter is provided on along the outer edge of the flange to collect the spilled fuel, and this gutter has a number of openings to conduct the fuel from the gutter to the exterior.
Preferably, in addition to the depression, a number of semicircular grooves which open in one direction should be provided on both sides of the depression in order to collect the spilled fuel.
It is also desirable that the gutter on one side of the tank down which the spilled fuel discharges should be segmented by ribs and one of the openings described above should be provided for each segment between the ribs.
The aforesaid fuel tank would be ideally suited for use with a general purpose engine.
In other words, this sort of engine has a fuel tank on top of the engine comprising an upper portion with a fuel inlet on its top and a lower portion which is mounted to the engine body. A recoil starter is placed on the end of the crankshaft. This engine is distinguished in the following way. On top of the upper portion of the fuel tank is a depression which contains the area around the fuel inlet and which slants downward toward the recoil starter. A gutter is provided along the periphery of the flange, and the openings in the gutter which lead the spilled fuel to the exterior are provided in the side of the recoil starter.
With this configuration, it is advisable to provide a number of semicircular grooves on the upper portion of the fuel tank which open to the recoil starter side. These grooves should be on the portion of the surface other than the depression on the surface of the tank in order to collect the spilled fuel effectively.
Furthermore, on the upper half of the tank, at least the portion of the gutter on the side of the engine where the recoil starter is located should be separated by ribs and one of the openings should be provided in each segment created by the ribs.
With this invention, any fuel which happens to drip onto the upper surface of the fuel tank during fueling will discharge primarily in one direction, namely, into the depression which opens onto the recoil starter. The spilled fuel will then enter the gutter along the flange and be conducted to the exterior via the openings in that gutter.
The fuel tank should be mounted on the body of the general purpose engine so that the portion of the gutter facing the recoil starter side is slightly lower than other portions of the gutter to conduct the spilled fuel to the recoil starter side.
In this general purpose engine, a generator or working machine is connected to the output shaft, and a muffler, which can be extremely hot, is installed above the shaft. With this invention, the gutter is located above the recoil starter, which does not reach extremely high temperatures or contain any troublesome components. Any spilled fuel which drips down off the top of the fuel tank is guided toward the recoil starter. This enhances the safety of the engine.
Fuel which traverses the top of the upper portion of the tank at a right angle to the direction in which it exits the depression (i.e., toward the recoil starter) will discharge into the semicircular grooves, which will conduct it toward the recoil starter. It will then discharge into the gutter and be discharged to the exterior through the openings.
With this invention, then, any fuel which spills on top of the fuel tank discharges through the depression and semicircular grooves and collects in the gutter along the flange. It is discharged through multiple openings toward the relatively cool recoil starter. The fuel travels horizontally along the flange which joins the upper and lower halves of the tank, such that it never comes in contact with the hot cylinder or any electrical components. This design eliminates the danger of fire and the possibility that any of the electrical components will fail.
The gutter is segmented by ribs, so that even if a large volume of fuel discharges into it, the ribs will prevent the fuel from discharging along the periphery of the flange, and it will be discharged through the openings. The fuel thus discharges out of the gutter through the openings without having a chance to flow out over the flange.
According to this invention, the flange is a ribbed flange which extends along the entire periphery between the upper and lower halves of the tank. These halves should be welded at the web of the ribbed flange.
With this invention, the ribbed flange enhances the circumferential rigidity of the fuel tank and allows the gutter to function as a discharge route for the fuel.
The upper and lower portions of the fuel tank in this invention can be formed of a synthetic resin material.
With this invention, a thicker resin material can be used without increasing the weight in comparison with a metal sheet. The semicircular grooves increase the rigidity of the upper portion of the tank; the resulting strength allows realization of a fuel tank virtually free of vibration and noise.
This invention is a fuel tank of the sort in which an upper and lower portion, each of which has a virtually square surface, are joined at a flange, and in which the fuel inlet is in the center of the top of the upper portion.
This fuel tank is distinguished by the following. The upper and lower portions are formed from a resin. The upper portion has a depression in its center which contains the fuel inlet. The cross section of this depression is a trapezoid, one side of which is open and slopes downward. From the center, its upper surface is inclined in one direction toward its outer edge by a specified amount to form a convex surface. On either side of the depression and oriented along the same axis are a number of grooves which open onto the same edge.
The two halves of the tank are welded at the web of a ribbed flange which extends along the entire periphery between the two halves.
It is desirable that the grooves should have a semicircular cross section, and that multiple grooves be provided.
According to this invention, a gutter is provided along the entire periphery where the ribbed flange of the upper portion meets the outer surface of that portion. At least the portion of this gutter on the side of the tank where the fuel runs off is segmented by ribs and an opening to the exterior is provided in each segment created by the ribs.
With this invention, any fuel which happens to drip onto the upper surface of the tank during fueling will discharge primarily into the trapezoidal depression with the slanting bottom. The spilled fuel will then discharge into the gutter along the flange and be conducted to the exterior via the openings in this gutter.
Fuel which traverses the top of the upper portion of the tank at a right angle to the direction in which it exits the depression will flow into the semicircular grooves, which will conduct it toward one side of the tank, the side where it will be discharged. It will then discharge into the gutter and be discharged to the exterior through the openings.
With this invention, then, any fuel which splashes or drips onto the top of the upper portion of the tank will discharge into the trapezoidal depression or the semicircular grooves on either side of it. It will then flow toward the lower end of the depression or grooves and fall into the gutter along the flange, where it will also seek the lowest point. The fuel will then be discharged through the openings provided. Spilled fuel will travel along the flange, such that it will never come in contact with the hot cylinder or with any electrical component.
The gutter is segmented by ribs, so that even if a large volume of fuel discharges into it, the ribs will prevent the fuel from discharging along the periphery of the flange; instead, it will be discharged through the openings. The fuel thus has no chance to travel horizontally around the tank.
The upper and lower halves of the tank are formed from a resin, so a thicker sheet can be used without increasing the weight over that of a similar quantity of sheet metal. The semicircular grooves on either side of the trapezoidal depression increase the rigidity of the upper portion of the tank; the resulting strength significantly reduces the vibration and noise experienced by the tank.